Various types of machinery or power-driven tools, such as a band saw, employ a driving pulley and a driven pulley. The driving pulley is connected to a motor, and the driven pulley guides the saw band or a similar implement for movement between the pulleys. Means are provided for supporting the driven guiding pulley and for properly tensioning the saw band between the pulleys; and further means are provided for pivoting the guiding pulley about an axis transverse to its rotational axis, thereby facilitating an alinement of the guiding pulley and hence the saw band. In the prior art, of which I am aware, the supporting and alinement means have been generally adequate for the purposes intended, but mostly have been relatively sophisticated or complicated mechanisms and hence expensive to produce and difficult to assemble. In addition, the supporting and alinement means resorted to in the prior art do not offer the desired degree of lateral support consonant with an inexpensive mechanism for high-volume power tools intended for consumer usage.